Return bend



Feb. 28, 1939. F. E. KEY

2 Sheets-Shet 1 Filed Nov. 20, 1936 F. E. KEY

F eb. 28, 1939.

RETURN BEND Filed Nov. 20, 1936 2 Shee gs-Sheet 2 Patented Feb. 28, 19.39

RETURN BEND Frederick E. Key, St. Louis, Mo., assignor, by

mesne assignments, to Reconstruction Finance Corporation, St. Louis, Mo., a corporation of the United States of America Application November 20, 1936, Serlal No. 111,834

1 Claim.

The fundamental object of the invention is to provide a return bend assembly in which the joints between the ends of the connecting'memher (or U-bend) and the tubeends may be made gas-tight and secured in this position under the adverse conditions of oil cracking stills.

One of the objects of this invention is to provide means for holding sectional collars together and in alignment and to prevent relative spreading, lateral movement and twisting while permitting limited relative longitudinal movement, in that type of return bend assembly in which flanges on the U-bend are secured to the collars and the collars engage shoulders onthe tubes.

Another object'of the invention is to provide a novel bushing on the ends and at the face of the U-bend and including that portion intended to contact the tube ends, thus providing for the ready repair of the U-bend at its place of major wear. I

Another object of the invention is to provide a U-bend assembly in which the bolts or clamping means are so constructed and arranged that leaks due to unequal cooling of the U-bend parts may be eliminated or reduced.

Other objects of the invention will be apparent from the following description, taken in connection withthe accompanying drawings.

Fig. 1 is a side elevation partly in section, taken approximately on line II, Fig. 2, showing a return bend assembly embodying the invention;

Fig. 2 is an endview;' and,

Fig. 3 is a section on line 3-3, Fig. '1.

A U-bend or connecting member I has its ends engaging the ends of tubes 2 and 3 to form a communication between the tubes. The joint betweenthe tubes and the U-bend is formed by an annular ridge 4 at the end of each tube which engages in-an annular groove 5 formed in the face of each of the ends of the U-bend.

The tubes are seamed to the U-bend by means which include flanges 6 about each end of the bend and sectional collars 1, each having an internal annular groove 8 to receive a circumferential flange 9 about the tube near its end. Bolts or studs Illconnect the flanges 6 and the collars 1 To hold the sections of the collars together and' in proper bores in a link 12. The arrangement is such that the collars 1 and thereby the tubes 2 and 3 are held substantially against relative lateral, spreading or twisting movements, whereas relative longitudinal or parallel motion is permitted. i

To limit the relative longitudinal movement of the collars 1 a set screw I3 is threaded in the link l2 and has a head which, for economy of space, is positioned in a socket or sockets M in the collars but which is adapted to engage the shoulders l5 at the bottom of the socket H. The set screw i3 is not tightened completely against the bottom of the socket but the bottom of the head is allowed to remain slightly above the bottom of the socket I4, as clearly shown in Fig. 1. This permits a relative but limited longitudinal movement between the parts.

The bolts ID are hollow and passageways iii are provided in the link I! to register with the holes through the bolts I01 Thus a circulation of air through the bolts is permitted to keep them as cool as practicable and prevent spreading at the joint between the U-bend and the tubes.

Preferably, a bushing [1 as shown in Fig. 1 is inserted by a pressed fit in each of the two bends.

The outer face of the bushing is flush with the is particularly adapted to that form of construction in which removable plugs are provided in line with the bores of the tubes for access in cleaning the tubes. With such a type of connection it is unnecessary to remove the return bend v,for cleaning. The construction and arrangement of the plugs are best shown in Fig, 1. The U-bend I has openings l8 in axial alignment with the tubes when the U-bend is in place and are closed by plugs IS. The U-bend is provided with outward extensions 20 concentric with the openings I8 and are threaded to receive a jamb nut 2| which holds the plugs IS in position. The particular construction of the plug and its sealing members are no part of this invention, but will be clearly understood 'by those skilled in the art from the accompanying drawings.

The bolts ID are arranged as close to the openings of the tubes as is practicable. To this end the bolts III are provided with circular nuts 22 having polygonal sockets to accommodate a wrench. To provide abolt which may be readily removed and which at the same time can be properly tightened, the bolt I0 has on one end Acme threads to engage similar threads in holes ona collar 1. The outer end of the bolt [0 is provided with S. A. E. threads for engagement with internal threads on the nut 22. Bolts used in such environment are apt to gall and stick necessitating their being cut when removed. The Acme threads, which are of high pitch, provide for the ready removal of the bolt, while the S. A. E. threads, being of low pitch, enable the device to be properly tightened.

The circumferential flange 8 on the tube has: an outer as well as an inner shoulder, as clearly shown in the drawings Fig. 1. This necessitates: the collar I being formed in two or more parts, as clearly shown in Fig. 3. The inner shoulder forms an abutment for the collars in order that the collars may hold the tubes in engagement with the return bend. The outer shoulder enables the collars to hold the tubes in assembly when the return bend is removed.

The link l2, as previously described, is of substantial thickness and hasa pair of accurately machined holes to receive the shanks ll of the collars 1. Thus when the link I2 is brought into position so that the shank ll of the collar 1 is in an opening in the link the two sections of the collar 1 will be held in proper position and when While longitudinal movement is permitted, still it is desirable to limit the amount of that-lon itudinal movement so that when the U-bend is oil,

- the tubes will nevertheless be held approximately movement is permitted so that the joints between i the U-bend ends and the-tube ends may be made properly without distortion of the U-bend, notwithstanding minor imperfections due to tolerances permitted in manufacture,- and due to wear or use. It will also be apparent that the arrangement of the collars and the link are such as t permit one tube in a pair to be replaced without disturbing the other tube.

From the foregoing description it will be seen that the invention accomplishes its objects. Parts of the invention may be used without the whole and various changes may be made in the details of construction, within the scope of the appended claim, without departing from the spirit of this invention.

I claim:

In a return bend assembly a U-bend, an annular flange about each end of the U-bend, a pair of collars adapted to engage shoulders on tubes to be connected to said U-bend, bolts having longitudinal bores therethrough for connecting said flanges and collars and adapted to be threaded in holes through the collars, and a link for said collars positioned adjacent the inner ends of said holes through the collars and having holes therethrough positioned to register with the bores through the bolts to allow a circulation of air through the bolts.

' FREDERICK E. KEY.- 

